The invention relates to methods and tools used in knee arthroplasty. More particularly, the invention relates to methods and tools used in knee surgery where artificial femoral and tibial components are installed.
Total knee arthroplasty involves the replacement of portions of the patellar, femur and tibia with artificial components. In particular, a proximal portion of the tibia and a distal portion of the femur are cut away (resected) and replaced with artificial components.
As used herein, when referring to bones or other body parts, the term “proximal” means closest to the heart and the term “distal” means more distant from the heart. When referring to tools and instruments, the term “proximal” means closest to the practitioner and the term “distal” means distant from the practitioner.
There are several types of knee prostheses known in the art. One type is sometimes referred to as a “resurfacing type”. In these prostheses, the articular surface of the distal femur and proximal tibia are “resurfaced” with respective metal and plastic condylar-type articular bearing components.
The femoral component is a metallic alloy construction (cobalt-chrome alloy or 6A14V titanium alloy) and provides medial and lateral condylar bearing surfaces of multi-radius design of similar shape and geometry as the natural distal femur or femoral-side of the knee joint.
One important aspect of these procedures is the correct resection of the distal femur and proximal tibia. These resections must provide planes which are correctly angled in order to properly accept the prosthetic components. In particular, the resection planes must be correctly located relative to three parameters: proximal-distal location, varus-valgus angle, and flexion-extension angle.
Moreover, following distal resection, the femur must be shaped with the aid of a cutting block. The cutting block must be correctly located relative to internal-external rotation, medial-lateral position, and anterior-posterior position.
Recently, various computerized systems have been introduced to aid the practitioner during different surgical procedures. A typical system is described in the attached Appendix.
These systems include multiple video cameras which are deployed above the surgical site and a plurality of dynamic reference frame (DRF) devices, also known as trackers, which are attached to body parts and surgical instruments. The trackers are generally LED devices which are visible to the cameras. Using software designed for a particular surgical procedure, a computer receiving input from the cameras guides the placement of surgical instruments.
The prior art instruments used for determining the correct planes for tibial and femoral resection in total knee arthroplasty are not well suited for use with computerized systems. The known tools utilize either intramedullary alignment or extra-medullary alignment and adjustment of the degrees of freedom simultaneously is difficult or impossible. Moreover, in order to be useful with computer aided navigation systems, trackers must be attached to the tools. Existing tools do not permit the attachment of trackers.